Refining fatty oils and fats



Patented Apr. 26, 1938 UNITED ST TES PATENT OFFICE mt FATTY OILS AND FATS Edward M. James, Moylan, Pa, asslsnor to The Sharples Specialty Company, Philadelphia, Pa a corporation of Delaware '80 mm. Application mm." 19, 19:1,

SerialNo. 511,112

1 Clalm. (CI. 87-12) 1 coloring matters without undesirably affecting oils being refined and while minimizing losses of oil in the purification process. It is a further purpose of this invention to purify oil by means which will make the resulting product edible.

Oils have heretofore been refined by treatment with caustic soda solution. This method of refining has, however, been found objectionable since neutral fatty acid glycerides are attacked by the caustic soda, forming soap and glycerine with consequent undesirable loss of finished neum tral oil. Further loss of oil in such process is occasioned by oil being mechanically entrained in precipitated soap and being removed along with removal of the soap. I

It is an advantage of this invention that oils are refined substantially without breaklng'up of the fatty acid glycerides and loss of finished neutral oil. It is a further advantage of this invention that means are employed which tend to break emulsions and which by so doing reduce losses of oil because of oil becoming entrained in substances which are separated from the finished oil. a

This invention is applicable to the refining of a great variety of different oils. It is, for example, applicable to the refining of vegetable'oils. Without imposing limitations on this invention, the following vegetable oils: may be mentioned, namely, cotton seed oil, linseed oil, rapeseed oil,

40 peanut oil, soya bean oil, cocoanut oil, sesame oil, palm oil, palm' kernel oil, castor oil and olive oil. Animal oils may also be purified according to this invention, for example, tallow, fish oil, whale oil, neat's-foot oil, lard oil,.lard and butter n.

The term fatty oil as used in the specification and claim is given a broad interpretation covering substances which comprise the glycerides of fatty acids saturated and unsaturated and as includingsuchsubstancesastallowandlardabove mentioned that are sometimes called fats.

I have found that trior di-sodium phosphates may be advantageously used in the refining of fatty oils. While I regard the use of these substances as, preferable other triordi-alkali metal salts of phosphoric acid such as trior di-potasslum phosphate and trior di-lithium phosphate may also be used according to this invention. a For purposes of convenience in description, however,

this invention will be described using the sodium salts of phosphoric acid as illustrative thereof. As distinguished from the mono-salt of phosphoric acid.'the phrase poly-salts will be used. Thus-triand/or di-sodium phosphate will be referred to as poly-sodium phosphate.

The term poly-sodium, or poly-alkali metal phosphate isv to be regarded as including compounds such as pyrophosphate. For example sodium pyrophosphate, Nail-":01, may be used according to this invention. Moreover, it is to be understood that it is within the scope of this invention to use poly-alkali metal phosphate mixed with other substances. For example, tri-sodium phosphate can be used with caustic alkali such as sodium hydroxide, and the advantages of this invention partially realized.

In the practice of this invention, fatty oils may be refined by mixing therewith an aqueous solution of poly-sodium .phosphate. Where, for ex-' ample, a fatty oil is treated with an aqueous solu- 25 tion of poly-sodium phosphate, free fatty acid present in the oil will react to-iorm soap which may be readily separated from the oil. Moreover, the coloring matter is brought into a form which renders it likewise readily separable. As an aqueous residue is formed which may comprise soap, coloring matters, phosphate and water and which is immiscible with oil, these substances can be readily separated from the oil by difference in J gravity or other suitable means.

While the reactions between fatty acids and triand di-sodium phosphate are not proven, they are believed to be as follows:

(1 non aro. aom+ H.0'+Ns ,n1 o.

fatty acid tri-sodium soap water di-sodium I phosphate phosphate 2 non +NssHPOHBONs-i- H,o+ mnlroi fatty acid di-sodium soap water mono-sodium 9m phosphate It is of great advantage in theuse of tri-- or di-sodium phosphates according to this invention that they do not attack to any substantial degree the neutral 'glycerides of oil and effect losses thereof. Moreover, both poly-sodium phosphates as originally added and the lower phosphates into which they are resolved by reaction with the fatty acids serve to break up emulsions and prevent oil from being entrained with soap. and thereby lost upon removal ofthe soap. This latter property is believed to be due to the fonimtion of the phosphates.

It has been found that where tri-sodium phosphate is used alone and there is a substantial excess thereof, e. g. about 50% excess, that only the first reaction as above written takes place and that the di-sodium phosphate produced does not further react to form substantial amounts of mono-sodium phosphate. Where, however, thereis not a substantial excess of tri-sodium phosphate present, the tri-sodium phosphate will first react to form soap and di-sodium phosphate, and the di-sodium phosphate will then react to form further soap and mono-sodium phosphate. If di-sodium phosphate is used initially only the second reaction above set forth will occur. It is obvious from the above that a given amount of tri-sodium phosphate is more effective in saponifying free fatty acid than would be a corre- & sponding amount of di-sodlum phosphate. It is ordinarily preferable therefor to use tri-sodium phosphate.

The amount of poly-sodium phosphate which it is desirable to use according to this invention de- 35 pends upon the amount of free fatty acid contained in the oil to be refined. In the usual case, it is preferable to add about 50% of poly-sodium phosphate in excess of that theoretically needed to complete the reaction with the free fatty acid.

' Where oils being refined contain free fatty acids running about 1% to 5%, which is the usual case, e. g., prime cotton seed oil, it is reasonably safe to assume that the oil contains 5% free fatty acid and then use double the quantity of poly-sodium phosphate which would be necessary theoretically to react therewith. While a number of different free fatty acids may be contained in an oil which taken separately would have different molecular weights, I have found that it is convenient and reasonably accurate to assume that the molecusubject to considerable variation.

50 invention has been said to comprise first mixing poly-sodium phosphate with water and then adding a solution of the two substances to fatty oil, it is to be understood that this invention comprises more broadly the mixing of fatty oil, water and poly-sodium phosphate together, regardless of the order in which they are mixed.

The amount of free fatty acid in an oil maybe more accurately determined, if this is desired, by titration methods, as by titrating a sample of 50 the oil against tenth normal sodium hydroxide.

The preliminary determination of the fatty acid content of oils is particularly desirable in the case of oils which may have higher fatty acid content than 5%. Some oils have been found to have as high fatty acid content as or even 60%. Where the fatty acid content of the oil is thus determined, then ordinarilyit is desirable to use sufilcient phosphate so that there will be about 50%excess thereof. a

As increased amounts of phosphate are necessary in treating oils having a relatively high percentage of free fatty acids, increased amounts of water become necessary in order to dissolve therein the phosphate which is used. As the use of excess amounts 'of water is disadvantageous, it

may be desirable, where oils of high fatty acid content are treated, to decrease the excess of phosphate that is used so that the necessary amounts of water will not be too great.

In refining fatty oil according to this invention, the mixture of oil and phosphate solution is preferably heated in order to promote the reaction. The temperature which is most advantageous varies somewhat with different oils. Temperatures, for example, of about 60 F. or 70 1'. have been found advantageous in the refining of cotton seed oil, soya bean oil, and peanut oil. For cocoanutand palm oils, for example, temperatures of about 80 F. to 90 F. have been found advantageous. It is ordinarily preferable to gradually increase the intensity of heating during the process from the temperatures above given so as to finish at temperatures such as 110 F. to 140 1". While it is normally preferable to avoid excessive heating, the oil should be sufficiently heated at least to get it into a liquid condition. In the treatment of oils according to this invention, it is preferable to first mix the oil with the phosphate solution and then heat the mixture of oil and solution.

It is preferable to subject the mixture of fatty oil and poly-sodium phosphate solution to agitation as the desired reaction and result is promoted by so doing.

This invention may be employed using either continuous or batch operation. Mixing, agitating and heating operations may be continuous or batch. Moreover, the separation of soap, coloring matter, phosphate and water from the remaining oil may be continuous or batch.

For example, this invention may be carried out by mixing phosphate solution with an oil to be refined, and then agitating and heating the mixture to a temperature appropriate to the oil in a batch operation and then effecting continuous separation of the aqueous mixture of soap, water and phosphate from the finished oil by means of a high speed centrifugal separator. Moreover, it is also possible to continuously feed oil and Poly-sodium phosphate solution inproper proportion in a mixer, and then continuously run the mixture through means for heating and agitating the same to permit the desired reaction to take place. The aqueous mixture of soap, coloring matter. and phosphate may then be continuously separated from the oil by a centrifugal separator as above stated. Not only may separation be effected by centrifugal force, but other means of separation may also be employed such as gravity settling in a settling tank.

Where oil is purified according to this invention, it will be found that the free fatty acids have been saponified and removed and that undesirable coloringv matter will. for the most part, also have been removed. It will also be found that the loss in oil, will be much less than losses occasioned in refining oil according to methods heretofore practiced. 'While the resulting oil after treatment may be slightly colored due to the fact that a small proportion of the coloring matter may have been retained, this does not detract from the quality of the product. Oils treated according to this invention will be found to be. edible.

While specific examples of the invention have been given above. it is to be understood that this has been done merely for purposes of illustration and the true scope of this invention is not to be considered as limited thereby.

I claim: tained in the oil, heating the mixture to 60 to 70' A process 01' refining soya bean oil that con- I". while agitating. B 106118-8108 the t sists in mixing with the son bean oil a saturated D n t0 to 4 1. and thereafter cenaqueous solution of trisodium phosphate in an" trii'uzinz the mixture to S pa ate the aqueous 5 amount approximately 50% in excess oi that 911886 from the r te necessary to neutralize the tree fatty acids con- EDWARD M. JAMES. 

